A foundation is $2$m deep. A rectangular footing is $2$m x $3$m in plan. The soil supporting the footing has a friction angle of $32$ degrees and cohesion of $20$ kn$/$m$^2.$ The unit weight of the soil is $17$ kn$/$m$^3.$ Determine the allowable gross load in the foundation assuming a factor of safety of $3$ and general shear failure occurs in the soil. Use Terzaghi's equation.